The forest department has decided to radio-collar ten tigers in the Sunderbans where population dynamics of the big cats has al ways remained a mystery. And this time, an advanced set of radio collars, which helped scientists track tigers in Nepal and lions in Gir, will be used in the mangroves.

A team of Wildlife Institute of India (WII) officials, led by senior scientist Y V Jhala, is likely to visit the mangroves in April for the first leg of the exercise. However, a forest department official said the number of tigers to be collared during their first visit will only be decided after consulting the WII scientists. “The dates for their visit is yet to be finalized,” said the official.

It may be noted that a total of five tigers, two adult females and three adult males, were radio-collared by the WII scientists in the Sunderbans in 2010. Satellite collars were used for this purpose. Sources said radio-collaring helps experts gauge the home range of tigers , which in the long run comes handy in establishing the density of the big cats in a forest. The study had then revealed that the tigers’ home ranges hovered between 190 to 200 square kilometres.

Though large home range indicates lesser density, as a tiger’s home range depends on prey base and territory of other tigers, in Sunderbans the exercise didn’t yield the desired result then as several collars stopped working within a few days of its deployment.

WII’s Y V Jhala said that some data on the tigers’ home range and territory could not be established then. “But this time, we have made some changes in the circuitry of the satellite collars to make these robust ones. We have used these collars on lions at Gir and they have even functioned at a stretch for a year. So, this time we expect to get a more reliable data,” he said, adding that they are hoping to collar all the ten tigers in a year’s time.

However, the exercise then managed to establish the fact that there is tiger movement between the Indian and Bangladesh Sunderbans. “The Khatuajhuri male, which was a stray animal, had crossed the Harinbhanga river to enter the Talpati island of Bangladesh Sunderbans,” revealed a WII scientist.

Tracking of the radio-collared tigers had also revealed that there was a general trend of higher movement rate by the mangroves tigers during the day time. However, soon after this study the WII scientists decided to radio collar a minimum of 10 tigers, of which 4-6 in a contagious area of 300-400 square kilometres, to understand home range overlap and territoriality. “The exercise to be conducted now will help the scientists understand whether and how Sunderbans tigers protect their territory,” said an official.

Meanwhile, the camera trapping exercise, being done jointly by the forest department and WWF-India, is complete in two ranges of the mangrove’s — Sajnekhali and National Park East. “The exercise is on at the Basirhat range. We will start withdrawing the cameras laid at Basirhat from April 11 and hope to give a density for the entire tiger reserve area by the end of April,” said WWF-India’s Sunderbans chapter head Anurag Danda. After identification, the photographs will be sent to the National Tiger Conservation Authority, so that the Sunderbans tigers can be counted in the UID-type databank.